The hemotrophic bacterium Bartonelta bacilliformis, is the causative agent of two distinct clinical syndromes known as Oroya fever and verruga peruana. The Oroya fever syndrome is characterized by the presence of the organism on and inside erythrocytes. Verruga peruana is the tissue phase of the disease in which hemangioma-like lesions can be found on the face and lower extremities due to the presence of the organism inside endothelial cells and the pronounced cell proliferation. Our long-term goal is to understand the role of important ligand-receptor interactions that mediate attachment of the organism to host cells and promote cell invasion. The objective of this application is to determine the role of a protease-adhesin in BartonelIa attachment and invasion. The central hypothesis is that this protein which is surface-exposed on Bartonella mediates the binding of the organism to host cells and subsequent internalization. The hypothesis has been formulated based on strong preliminary data which suggest that this protein interacts with commercially purified integrin proteins and human plasma fibronectin that are involved in a variety of cell adhesion phenomena. The rationale for doing this research is that new innovative approaches and strategies for prevention and treatment of Bartonella infection will be possible once we have a better understanding of Bartonella/host cell interactions. The central hypothesis will be tested and the objective of the application accomplished by pursuing three specific aims: 1)To isolate the protease-adhesin by anion exchange chromatography of detergent extracts ; 2) To characterize the interactions between the purified protease-adhesin and host cells and extracellular matrix proteins utilizing radiolabeled binding and invasion assays and enzyme-linked immunosorbent assays; and 3) To clone the gene encoding the Bartonella protease-adhesin utilizing immunological screening of a lambda ZAP B. bacilliformis genomic library and blue/white color selection of recombinant clones.